Android Room Database DAO debug log

Question

Given a Room database DAO like this:

import android.arch.persistence.room.Dao;
import android.arch.persistence.room.Query;

import java.util.Date;
import java.util.List;

@Dao
public interface MyDao {

    @Query("SELECT * FROM MyTable")
    List<MyItem> all();

    @Query("SELECT * FROM MyTable WHERE date = :date AND language = :language")
    MyItem byDate(Date date, String language);


}

Is there a way to have a Logger or something like that added to MyDao so that I could see which statements are being performed. This would be really helpful during development, because I could immediately check if the functions are transformed correctly to the expected SQL statement or not.

Answer 1

Assuming that Room uses framework's Sqlite as underlying database, the statements can be quite simply logged. The only limitation: this can be done only on emulator.

From SQLiteDebug.java:

/**
 * Controls the printing of SQL statements as they are executed.
 *
 * Enable using "adb shell setprop log.tag.SQLiteStatements VERBOSE".
 */
public static final boolean DEBUG_SQL_STATEMENTS =
        Log.isLoggable("SQLiteStatements", Log.VERBOSE);  

---

By default, the log.tag.SQLiteStatements's value is not set:

alex@mbpro:~$ adb shell getprop log.tag.SQLiteStatements
<-- BLANK LINE -->

According to the above documentation, to set the property we have to use:

alex@mbpro:~$ adb shell setprop log.tag.SQLiteStatements VERBOSE
alex@mbpro:~$ adb shell getprop log.tag.SQLiteStatements
VERBOSE

As we can see, the VERBOSE value was successfully set. However, if we'll re-run our application - we won't see those statements printed. To make it work, we'll have to restart all the services using adb shell stop and then adb shell start.
If you'll try to do that with a regular device, you'll receive the following error (tried with Pixel XL / stock Android 9):

alex@mbpro:~$ adb shell start
start: must be root
alex@mbpro:~$ adb root
adbd cannot run as root in production builds

This is why we have to use the emulator:

alex@mbpro:~$ adb root
restarting adbd as root
alex@mbpro:~$ adb shell stop
alex@mbpro:~$ adb shell start

The emulator will restart.
Run your application and you'll see similar Sqlite statements in logcat:

<redacted..>
V/SQLiteStatements: <redacted>/my_db: "BEGIN EXCLUSIVE;"
V/SQLiteStatements: <redacted>/my_db: "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)"
V/SQLiteStatements: <redacted>/my_db: "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, "3cb5664b6da264c13388292d98141843")"
V/SQLiteStatements: <redacted>/my_db: "CREATE TABLE IF NOT EXISTS `MyTable` (`id` TEXT NOT NULL, `date` INTEGER, `language` TEXT, PRIMARY KEY(`id`))"
<redacted..>
V/SQLiteStatements: <redacted>/my_db: "BEGIN EXCLUSIVE;"
V/SQLiteStatements: <redacted>/my_db: "PRAGMA temp_store = MEMORY;"
V/SQLiteStatements: <redacted>/my_db: "PRAGMA recursive_triggers='ON';"
V/SQLiteStatements: <redacted>/my_db: "CREATE TEMP TABLE room_table_modification_log(version INTEGER PRIMARY KEY AUTOINCREMENT, table_id INTEGER)"
V/SQLiteStatements: <redacted>/my_db: "COMMIT;"
<redacted..>
V/SQLiteStatements: <redacted>/my_db: "SELECT * FROM MyTable"
V/SQLiteStatements: <redacted>/my_db: "SELECT * FROM MyTable WHERE date = 1551562171387 AND language = 'en'"  

---

To undo the changes, use these commands:

alex@mbpro:~$ adb shell setprop log.tag.SQLiteStatements ""
alex@mbpro:~$ adb shell getprop log.tag.SQLiteStatements
<-- BLANK LINE -->
alex@mbpro:~$ adb shell stop
alex@mbpro:~$ adb shell start
alex@mbpro:~$ adb unroot
restarting adbd as non root